The present invention relates to a radio communication system employing Code Division Multiple Access (CDMA), a method of managing adjacent station information in the radio communication system, and a management apparatus for the method.
In a radio communication system employing CDMA, by switching a base station, which is a communication partner of a mobile terminal, as the mobile terminal moves, the mobile terminal can communicate continuously, even when it moves. Technology for switching base stations, namely handoff technology, is disclosed in detail, for example, in TSG-C C.S.0024-A V2.0 issued by 3GPP2.
Handoff technology includes soft handoff and hard handoff. In soft handoff, communication of a mobile terminal is continuous, while in hard handoff a momentary break exists in communication of a mobile terminal. Basically, the handoff technology is standardized such that hard handoff is performed when soft handoff for continuing communication cannot be performed. A handoff source base station (i.e. a base station from which communication with a mobile terminal is changed to another base station) uses information of one or more base stations adjacent to it in order to perform soft handoff to an adjacent base station. In other words, to perform soft handoff, information on base stations adjacent to each base station is required.
Such adjacent station information should be changed not only in cases where a new base station is installed but also in cases where a communication environment is changed. Basically, change of adjacent station information or the like is carried out by hand.
However, such an operation is a burden to a communication service provider. Thus, methods of automatically updating adjacent station information have been developed. For example, such methods are described in Japanese Unexamined Patent Laid-Open No. 09-284828 (hereinafter, referred to as Patent Document 1) and Japanese Un-examined Patent Laid-Open No. 2000-333232 (hereinafter, referred to as Patent Document 2). In CDMA, basically a mobile terminal monitors radio waves from base stations other than a base station with which communication has been established. Thus, in the techniques described in Patent Documents 1 and 2, a base station, which is communicating with a mobile terminal, acquires communication characteristic information of other base stations from the mobile terminal in question, and adds the obtained information to adjacent station information.